Peatlands and the Carbon Cycle

Peatlands and the Carbon Cycle—from Local Processes to Global Implications. The First International Symposium on Carbon in Peatland, held at Wageningen, The Netherlands, on 15–18 April 2007 〈http: //www. peatnet. siu. edu/CC07MainPage. html〉 Boreal and subarctic peatland ecosystems cover ~3% of the earth's land surface and store 15–30% of the world's soil carbon (200–400 Pg) as peat, which constitutes a greater soil C density per square meter than any other terrestrial ecosystem. This large C pool, in addition to carbon in arctic soils, lies at higher latitudes that will experience significant climate change over the next century. Tropical peatlands also contain large C reservoirs, the stability of which is threatened by ongoing land use change. At the 2005 Ecological Society of America/INTECOL meeting in Montreal, PEATNET (an NSF-supported Research Coordination Network) extended a general invitation for workshop proposals on peatlands. A small workshop to focus on peatland C cycling, proposed by Juul Limpens and Gabriela Schaepman-Strub, morphed into a meeting with 180 participants from 18 countries. The meeting goals were: (1) to advance our understanding of peatland C cycling through integration across disciplines and research approaches, and (2) to move toward a synthetic picture of the past, present, and future role of peatlands in the global C cycle and climate system, recognizing the potential for large feedbacks as consequences of projected changes in climate and in management and land use patterns. To foster a common understanding, plenary presentations introduced larger poster sessions on thematic areas including ecosystem biogeochemistry, microbial, plant, ecosystem, and landscape ecology, ecohydrology, paleoecology, and climate modeling, and large-scale assessment through spatial upscaling. Examples from boreal, subarctic, and cool temperate peatland research dominated the meeting, but there were also a few presentations on tropical and arctic systems. Common themes ran through the meeting. The presence of massive peat deposits is a testament to the long-term historical function of peatlands as net sinks for atmospheric carbon, and hence to global cooling on millennial scales. Nonetheless, the contemporary net C sink in individual peatlands displays a large interannual variability, and more broadly there may be geographic differences and differences among peatland types in the C sink strength. Whether peatlands globally function as a net carbon sink today remains uncertain. When methane emissions and their associated radiative forcing are considered, the magnitude and direction of peatlands' influence on climate is even less certain. Accumulating evidence indicates that peatland C balances are strongly influenced by drought, water table drawdown, and enhanced atmospheric N deposition, in some cases diminishing the size of the net C sink, or converting a peatland to a source of atmospheric C. Two challenges emerged from the meeting: (1) effective upscaling of net CO2 and CH4 emissions from plots and sites to regional and global scales, and (2) integration of peatlands into coupled carbon–climate modeling efforts. Most of the land surface schemes of global climate models that now include a formal representation of the C cycle do not include a realistic representation of the organic soils of peatlands. A few groups are working on this integration, but peatland researchers need to develop closer collaborations with the carbon–climate community to effectively incorporate peatlands into the next generation of earth system models. This integration needs to link peatland CO2 and CH4 cycling with ecohydrology, changing temperature regimes, changing atmospheric N deposition, ongoing permafrost melt, and fire impacts, the effects of which may differ among peatland types. PEATNET is sponsoring a workshop on Why is there Peat? , which will be held at Villanova University, 26–29 March 2008. The Second International Symposium on Carbon in Peatlands will be held in Prague, The Czech Republic, on 16–19 May 2009. Check the PEATNET web site for updates 〈http: //www. peatnet. siu. edu/〉 Information from the First International Symposium on Carbon in Peatlands is being disseminated through a special issue in the European Geosciences Union Biogeosciences Interactive Open Access Journal 〈http: //www. biogeosciences. net/specialᵢssue30. html〉